WASHINGTON—The Obama administration is working to reach a deal with Cuba by year’s end that would allow travelers to fly on scheduled commercial flights between the countries, U.S. officials say, chipping away at a travel ban without requiring Congress to lift it.

The agreement would allow airlines to establish regular service between the U.S. and Cuba as early as December, officials said, marking the most significant expansion of economic and tourism ties between the U.S. and Cuba since the 1950s, when Americans regularly traveled back and forth to Havana.

The Obama administration is also exploring further steps to loosen travel restrictions for Americans to the island nation despite the decades-old congressional ban, officials said.

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Only Congress can lift the long-standing U.S. travel and trade embargoes imposed against Cuba in the 1960s following the rise of Fidel Castro to power. But Mr. Obama has executive authority to grant exceptions to them. He announced several last December—such as allowing Americans to use credit and debit cards in Cuba and expanding commercial sales and exports between the two countries—and is considering others.

One way is to allow individual travelers to visit Cuba independently of a tour group, so long as they say their trip is intended to pursue cultural exchange, a practice known as “people-to-people” travel.

U.S. laws authorize citizens to travel to Cuba only for specific purposes, including business trips, family visits or the people-to-people exchanges. By loosening restrictions on those authorized categories of travel, the administration in effect can chip away at the travel ban.

“The one logical thing they could do is let individuals create their own people-to-people program and not force them to go on expensive package tours,” said William LeoGrande, a professor at American University who has written extensively about U.S.-Cuban negotiations. “If they do that and it’s possible to book an ordinary flight instead of go on a charter, lots more people would go to Cuba.”

Deepening both U.S.-Cuba economic relations and the two countries’ cultural and tourism ties is part of how Mr. Obama hopes to ensure that the move toward normalization doesn’t unravel under his successor.

The White House has taken the same approach to the nuclear deal with Iran, which Congress is set to vote on next month and is likely to be implemented by Mr. Obama exercising his veto authority.

The White House hopes Mr. Obama’s Iran and Cuba policies follow the same political trajectory as his health-care law. The idea, administration officials have said, is that like the health-care law, the Iran and Cuba initiatives will become so embedded in American policy over Mr. Obama’s final 18 months in office that undoing them would be too difficult.

The president’s policies on Cuba and Iran have been widely criticized by Republican candidates running to replace him, while most Democratic contenders, including former Secretary of State Hillary Clinton, support them.

“In the eyes of Barack Obama and Hillary Clinton, his former secretary of State, the Cuban people are suffering because not enough American tourists visit the country, when the truth is the Cuban people are suffering because they live in a tyrannical dictatorship,” said Sen. Marco Rubio (R., Fla.) in a speech in New York last week.

Other opponents say increasing American travel to the island would primarily benefit Cuba’s military and intelligence services. “Tourism to Cuba’s regime is what oil is to Iran,” said Mauricio Claver-Carone, a director of the pro-embargo U. S-Cuba Democracy PAC, on Monday.

Mr. Obama hopes that the re-establishment of U.S. relations with Cuba becomes so integral to American travelers and business leaders that it would be too politically risky for any president to revoke. That, in part, relies on expanding Americans’ access to the island nation.

At the same time, the White House is working to establish a bipartisan coalition to dismantle the U.S. embargo on Cuba, at least piece by piece—starting with the travel ban.

Travel from the U.S. to Cuba is up 35% since January, Secretary of State John Kerry said in Havana last week at a flag-raising ceremony at the U.S. Embassy. He told reporters Friday that he and his Cuban counterpart, Bruno Rodríguez, discussed further steps the U.S. could take to loosen travel and trade restrictions but cautioned that fully lifting the embargo would require Cuba to address human-rights concerns.

Sens. Jeff Flake (R., Ariz.) and Patrick Leahy (D., Vt.), who support Mr. Obama’s Cuba policy and have introduced a bill to lift the travel ban, are among supporters who want the administration do more to loosen restrictions on travel to the island nation.

“It makes no sense that Americans can travel freely anywhere in the world except Cuba, said Tim Rieser, foreign policy aide to Mr. Leahy, adding that the senator thinks new licenses for individuals to travel to Cuba “is what the American people want and deserve.”

The White House, many federal departments and the U.S. airline industry are aligned behind efforts to resume scheduled service to Cuba. With that sort of support, two officials involved in the negotiations said, they don’t see any roadblocks. “We’re committed to it, there’s good will on both sides and we’re continuing to talk,” one of the officials, who is at the State Department, said. A deal by year’s end “is certainly our hope.”

The other official, from the Transportation Department, added: “My own personal view is we can work through this. When that would happen is an open question.”

For decades, U.S. citizens with an authorized purpose to visit Cuba have generally taken charter flights that are allowed under an informal arrangement between the U.S. and Cuba.

The two countries now are working toward a similar arrangement to allow scheduled air service, which would enable authorized travelers to book flights to Cuba via U.S. airline websites or even travel sites such as Expedia.com.

The Obama administration’s revised rules on travel and commerce in Cuba lifted restrictions on scheduled air service between the two countries.

When those rules were implemented in January, the Transportation Department issued a notice that it planned to engage the Cuban government on resuming scheduled flights.

The new rules issued in January also eliminated the need for many authorized travelers to obtain prior U.S. approval, essentially letting them travel to Cuba on the honor system. U.S. citizens still need a Cuban visa to enter the country.

Still, traveling to Cuba for a cultural exchange—one of the 12 authorized purposes—requires going with a tour group. Proponents of expanded travel want Mr. Obama to allow individuals to travel alone to Cuba for “people-to-people” ties, or cultural exchanges.

Administration officials said Monday they are considering further steps to loosen travel and trade restrictions, but wouldn’t specify which were most likely.

“The people-to-people license put into effect in the first place was for individuals to meet with individual Cubans,” Mr. Flake said. “Going down and staying in a B&B which increasingly Americans are doing, riding in private taxis, eating in private restaurants—these are all acts we should encourage.”

In March, U.S. officials met with a handful of Cuban diplomats in Washington, where they agreed—through translators—that their countries’ 1953 “air transport agreement” was outdated, according to the State and Transportation Department officials. The U.S. officials proposed basic parameters for a new arrangement, including that any U.S. airline could serve Cuba as much as it wishes, one official said.

The Cubans said they would get back to the Americans. Last week, the Cuban government sent the U.S. negotiators a lengthy counterproposal in Spanish and a request to soon meet again, this time in Havana, one official said.

The negotiations are partly centering on how many flights a day would be permitted between the two countries and whether Cuba’s state-owned airline, Cubana de Aviación, can serve the U.S. The officials were doubtful U.S. laws would allow Cubana to fly to the U.S.

Many U.S. airlines, including
American Airlines Group Inc.
and
JetBlue Airways Corp.
, are eager to serve Cuba and have been pushing regulators to enable schedule service. Indeed, some carriers have already served the island for years by operating flights on behalf of charter companies.

American said it expects to operate 1,200 charter flights to Cuba this year, a 9% increase from 2014. On Tuesday, American plans to announce a charter from Los Angeles to Havana, its first Cuba service from the West Cost. “We’ve absolutely seen more demand,” said Howard Kass, American’s vice president of regulatory affairs.